Screw



Aug. 16, 1932. MUHUG 1,872,166

SCREW Filed Oct. 14, 1931 Patented Aug. 16, 1932 UNITED STATES LUDWIK Mll'HLIG, OF BIELSKO, POLAND SCREW Application filed October 14, 1931, Serial No. 568,768, and in, Germany November 6, 1930.

I have filed an application in Germany on the 6th November, 1980; in Poland on the 22nd January, 1981; and in Czechoslovakia on the 25th March, 1931.

The present invention relates to screws,

particularly for use on railway sleepers.

Wood screws are already known in which the thread is provided in proximity to the point of the screw with a groove of gradually 10 diminishing cross section, which groove causes a reduction of the triangular cross section of the thread towards the point of the screw by dividing the section into two triangular cross.

sections of smaller area. The triangular cross section of the thread proper, however, still retains the same length of base line from its starting point up to its termination, and it is only the height of the thread which diminishes towards the point of the screw.

The lmown wood screws are unsuitable for use on railway sleepers, inasmuch as when they are employed the compressing or forcing away of the wood only takes place at the tips of the threads. In consequence of its particular shape the thread of the known wood screw is operative principally at the point of the screw or screw bolt, whereas the head portion of the screw which does not exert a wedging action is less operative, although it is ust in proximity to the surface of the sleeper that the greatest eifects of the rain or snow, such as contamination, decaying the wood, etc., arise so that the maximum compression efiect exerted by the thread is required'at that part.

It is the principal object of the present invention to provide a screw, particularly for use on railway sleepers the cross section of the thread of which likewise decreases towards the point of the screw but which is free from the above-mentioned drawbacks. According to the invention the base line of the cross section of the thread, which may be of triangular, trapezoidal or other suitable shape, increases in length continuously from the point of the screw towards the head there-v of, whilst the pitch of the thread and the angle of inclination of the sides of the thread to the a screw thread of substantlally triangular base line remain. the same.

By this novel construction the result is obtained that in consequence of the wedging effect arising when the screw is screwed into the wooden sleeper, thescrew becomes more firmly seated in the wood, particularly at the base lines of thethread, and there is no possibility of the screw working loose. As the1 maximum wedging action takes place in proxlmlty to that part of the thread, the cross sectlon of which has the longest base line of the thread, i. e. at the end of the thread adacent to the head, the maximum action of the weather and atmosphere on the wood and on the screw which takes place atthe surface of the sleeper is most efficiently reduced. A preferred constructional form accordlng to the invention is illustrated by way of 55 example in the accompanying drawing, in which:

Fig. 1 is a front elevation of a screw according to the invention, and

Fig. 2 is a view of the profile of the screw thread to a larger scale. As can be seen from the drawing the base l1ne of the screw thread, which is shown by way of example as being of trapezoidal cross section, increases in length continuously from- B towards A, i. e. in the direction running from the point of the screw towards the head thereof, whilst the pitch of the thread and also the inclination of the sides of the latter remain unaltered. 0

Thenovel screws according to the invention can be manufactured in the hitherto customary manner by hot rolling methods.

I claim: 7 1. A screw, particularly for use on railway sleepers comprising in combination: a shank member; a head on said shank member; and a screw thread on said shank member of such form that the base line of the cross section of the thread increases continuously in length from the point of the screw towards the head thereof whilst the pitch of the thread and the angle of inclination of the sides of the thread to the base line remain the same.

2. A screw, particularly for use on railway sleepers, comprising in combination: a shank member; a head on said shank member; and

cross section on said shank member, the base line of the cross section of which thread increases continuously in length from the point of the screw towards the head thereof, whilst the pitch of the thread and the angle of inclination of the sides of the thread to the base line remain the same.

Signed at Warsaw, Republic of Poland, this thirtieth day of September, 1931.

LUDW'IK MUHLIG. 

